1. Field of the Invention
The present invention relates to a mining apparatus for the mechanized breaking-down of mineral raw materials, particularly coal, in underground mining operations. The mining apparatus includes at least one revolving endless chain and chain wheels for the endless chain at the revolving ends of the chain. A main drive is provided for one of the chain wheels and an auxiliary drive is provided for the other chain wheel. The main drive and the auxiliary drive each have a transmission unit including main transmission stage, initial transmission stage, coupling and drive motor. The mining apparatus is preferably a combined planing and conveying apparatus and, consequently, the endless chain is either a planing chain or a conveying chain.
2. Description of the Related Art
In mining apparatus of the above-described type it is desired that the drive motors of main drive and auxiliary drive run synchronously because only a synchronous running ensures a uniform load or maximum power of main drive and auxiliary drive. However, the drive motors do not run synchronously if the chain and the chain wheels are worn. This is because after a certain duration of operation, the endless chain runs on the chain wheels which have different pitch circles due to the wear. Thus, the endless chain runs on the chain wheels with different speeds. As a result, the load on the drive motor for the chain wheel on which the chain runs with the greater pitch circle may increase to such an extent that the other drive motor finally is pulled along in the manner of a generator. Accordingly, the other drive, i.e., either the main drive or the auxiliary drive, no longer operates as a drive as a result of the fact that the drives no longer run synchronously.
In order to avoid the resulting overload of the main drive or of the auxiliary drive, a drive control has become known by means of which the drive motors, generally asynchronous motors, are controlled directly. However, the control of drive motors with a power of up to 300 kW is cumbersome with respect to plant engineering, is expensive and, moreover, requires substantial space. This is particularly troublesome because of the narrow space available underground.
For this reason, frequently a different type of drive control is used. In this type of control, hydraulically driven and controlled motors act through auxiliary or support transmission units on the initial transmission stage of the main drive as well as of the auxiliary drive. Consequently, it is always necessary to use two special transmission units and two hydraulic motors. In addition, it is necessary to supply the hydraulic motors through hydraulic hoses. These measures also require substantial space and are expensive. Moreover, they are susceptible to trouble because, in view of the difficult work conditions prevailing in underground mining operations, it is possible that the hydraulic hoses are damaged. Moreover, hydraulic hoses can only be controlled downwardly and, when the hydraulic control fails, the entire mining apparatus can no longer be operated.
It is, therefore, the primary object of the present invention to provide a mining apparatus of the above-described type which avoids the disadvantages described above.
Specifically, it is the object of the present invention to provide a mining apparatus for the mechanized mining of mineral raw materials, particularly coal, in underground mining operations, which is of compact construction, is not expensive and includes a safely operating drive control for synchronous operation.